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Thyristor controlled 110V battery charger.

Started by Amod, Nov 11, 2022, 06:36 PM

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Iam making thyristor controlled regulated battery charger 110vdc output,230vac input and 30A.kindly help me how can i trigger thyristor using pic microcontroller and for self regulation how i can use feedback.I want to use 16f877A.

Please help


You can use MOC optocouplers with zero crossing to generate interrupt on change on Port B and start a timer to create the firing pulse after the required time. If you need current feedback then true RMS calculation of the chopped current waveform is necessary. Better is to take current feedback through a Hall sensor after the smoothening capacitor(if there is one)


Thanks sir,
One more thing ,can you guide me how to make soft start for charger.


John Lawton

I'm curious how a phase controlled charger would work. Are you switching full wave rectified DC into the battery using a thyristor? A little more detail on your hardware would be helpful please.


Rizwan s shaikh

Amod sar
1> Your using stapdown transformer
If using transformer what is voltage
2> your battery voltage


Quote from: John Lawton on Nov 13, 2022, 01:05 PMI'm curious how a phase controlled charger would work. Are you switching full wave rectified DC into the battery using a thyristor? A little more detail on your hardware would be helpful please.

John, maybe he is thinking of shifting the phase angle to 120 deg or more so that the peak of the phase controlled output is 220*1.414*0.5= 155V or less. Without transformer the load would be primarily resistive in nature so that commutation problems would not be severe even if he uses a fully controlled bridge to reduce ripple.
Dirty DC charging is supposed to be good for lead acid batteries


It is a long time since I worked with SCR's so I ran up a quick schematic using LTspice.
One method used was to switch on the SCR at the desired voltage on the waveform the SCR turns off when the voltage across it goes to zero or negative. This topology was often used in light dimmers and heating element control, due to RFI it may not be the best choice these days.

Re the waveforms.

Transformer T1 puts out 110VAC (155 volts peak).
The voltage is rectified by the fictitious ken diodes.

Waveform V(dc_raw) shows the rectified waveform.

Waveform V(N002,V to BATT) shows the timed gate drive pulse from V3 (normally a pulse gate transformer).

Waveform V(v_batt) is at V_to_BATT node. Note the voltage peak is 122V  (where the SCR turned on) not the 160V peak available from the rectifier circuit.

I(R1) is the current into the battery.

V2 and R1 represent a battery that reads 100V across its terminals and has an internal resistance of 5 ohms.

waveforms scr b.pngbatt charger scr b.png 


Here is the LTspice file, it includes some SCR models. BTW I do not guarantee any of the models are accurate they were downloaded from the WWW.

BTW this is for information only and needs work to produce a working design.

Download the test file change the .txt to .asc and run in LTspice (hopefully).

scr-battery charger b.txt

Ken Kranz


Thanks all for your help.
Iam postind details of battery charger.kindly see them.


1)Trickle charge-Battery charger for 200/250Ah battery:
Battery charger for 200/250Ah battery, the output
voltage of the charger shall be adjustable between
115 to 127 V (2.1 to 2.3 V per Cell) by a
potentiometer provided on the PCB for smooth step
less control of trickle voltage. In this mode the
charger will operate in constant potential mode with current limit.

2)Boost charge-Battery charger for 200/250Ah Battery:
Two rate of charging current shall be adjustable
between 10 to 30A through the potentiometers
provided on PCB. Starting rate of charging shall
run up to 130V (2.35 V/cell) and then with reduced
current of 50% of initial set value, finishing rate of
charging shall be upto 151V (2.75V/cell). After that
the charger shall be back in trickle mode. In trickle
mode, if trickle current goes upto 8 to 12 % of the
rated current (C-10 rating of the battery) excluding
steady load current (super-imposed load) on battery,
then the charger shall be change its mode from
trickle to boost. In this mode the charger shall be
operated in constant current mode.

3)The battery charger shall be designed in such a way that input supply variation in the
range of 170V to 270 V, the output for both trickle and boost charge condition shall not
result in an increase or decrease by more than +/- 2.5% of the preset value

4)The rectifier shall be of the half or full wave-controlled bridge connection using silicon
thyristors or silicon thyristors and diodes with liberal ratings.

5) A lead acid battery charger should switch to float charge when fully saturated
when operating in automatic mode.

6) Soft start feature shall be provided in the system.

7)Battery Charger shall have feature to communicate on MODBUS with SCADA
system for control (ON/OFF) battery charger, status monitoring, faults i.e. Battery
charger fail, input mains fail, input fuse fail/MCB trip, output MCB/MCCB trip/fuse
fail, DC over voltage, DC under voltage, earth leakage at RCC through SCADA
systems. The input and output voltage (Battery terminal and load terminal) of battery
charger shall also be communicated to RCC through SCADA.


A 30A 130V battery charge (3900W) is a reasonably large battery charger. I have included some links that may help.

BTW these days I would tend use FET's and PWM not thyrisors; a short circuit on the output is easier and quicker to deal with using FET's.



How can i control PWM using a potentiometer.pls guide.